Embattled city Comptroller John Liu is telling federal prosecutors to put up or shut up.

Even though his former campaign treasurer and a campaign donor face federal felony charges, Liu defiantly proclaimed he was “very proud” of his campaign and a staff that “has acted with the highest level of ethics.”

If that weren’t enough to throw down the gauntlet to Manhattan US Attorney Preet Bharara, Liu also asserted that the feds are dragging their feet on the investigation, and suggested they haven’t come up with much beyond unproven allegations.

“If there’s anything that my campaign is guilty of, or my supporters or my staff or, by extension, me — then prove it,” Liu all but dared Bharara on NY1 Wednesday night. The US Attorney’s Office declined to respond.

Liu’s campaign for mayor has been in turmoil since November, when fundraiser Xing Wu “Oliver” Pan was accused of funneling donations to the comptroller through straw donors to disguise the actual source of the funds, which turned out to be an undercover FBI agent.

In February, the campaign got another shock when 25-year-old treasurer Jenny Hou was slapped with similar charges.